[libsigc++2/variadic] filelist.am: Mention ptr_fun.h.

[Murray Cumming <murrayc src gnome org>]

commit f8136a129e43fa0008945887805770493d343d43
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Jan 7 17:39:14 2016 +0100

    filelist.am: Mention ptr_fun.h.
    
    I forgot to do this when I changed this from a a .h.m4 file to a .h file.

 sigc++/filelist.am |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/sigc++/filelist.am b/sigc++/filelist.am
index 6a77588..aa051a1 100644
--- a/sigc++/filelist.am
+++ b/sigc++/filelist.am
@@ -68,4 +68,5 @@ sigc_public_h =                               \
        adaptors/bound_argument.h       \
        functors/functor_trait.h                \
        functors/functors.h             \
+       functors/ptr_fun.h              \
        functors/slot_base.h